1. Field of the Invention
The present invention relates to exposure apparatus, exposure methods, and device manufacturing methods, and more particularly to an exposure apparatus and an exposure method used in a lithography process to manufacture microdevices such as a semiconductor device, and a device manufacturing method which uses the exposure apparatus or the exposure method.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (such as integrated circuits) and liquid crystal display devices, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper), or a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) is mainly used.
However, semiconductor devices will lead to higher integration in the future, and accompanying this, it is certain that the circuit pattern which should be formed on the wafer will be finer, and further improvement of the position detection precision of wafers and the like will be required in the exposure apparatus which is the mass-production apparatus for semiconductor devices.
For example, in U.S. Patent Application Publication No. 2006/0227309, an exposure apparatus is disclosed which employs a liquid immersion exposure method having an encoder type sensor (an encoder head) installed on a substrate table. In this kind of an exposure apparatus, liquid is supplied in a space between a substrate and an optical system so as to form a liquid immersion area, and the liquid immersion area may sometimes move from an area on the substrate to an area on the substrate table by the movement of the substrate table. In this case, there was a risk of the encoder head not functioning properly such as an output abnormality being generated in the encoder head, due to (the liquid forming) the liquid immersion area which covers the upper part of the encoder head (or the encoder head being buried in the liquid of the liquid immersion area).